CMU Robotics Alumnus Leads Development of Critical Landing Technology
By Debra Tobin
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"LVS Valid"
The message would sound cryptic to most people, but for Andrew Johnson, a principal robotics system engineer at NASA's Jet Propulsion Laboratory, receiving it from Mars on Thursday meant everything. It meant the Lander Vision System (LVS) developed by his team worked properly and that NASA's Perseverance rover landed safely on the red planet.
Andrew Johnson is a guidance, navigation and control engineer at NASA's Jet Propulsion Laboratory and is part of the team who worked on the Lander Vision System.
Johnson, who has worked at JPL since earning his Ph.D. from Carnegie Mellon University's Robotics Institute in 1997, has spent more than eight years developing the LVS. It was critical to successfully landing Perseverance within the rugged expanse of Jezero Crater, where it will gather rock and soil samples in a search for microbial life.
Computer vision played an unprecedented role in the landing, ensuring that the rover avoided such obstacles as boulder fields, dunes and crater walls in the final seconds of its seven-month journey to Mars.
"The landing was a huge milestone for me and my team," Johnson said. "All of our development work culminated in the landing, particularly the last 60 seconds."
Johnson studied computer vision at CMU under the tutelage of Martial Hebert, now dean of the School of Computer Science. It's a technology that he helped NASA employ on the Mars Exploration Rovers mission in 2004. In that case, though, computer vision was used to estimate motion, not determine the craft's position on a map.
Determining position is much harder, he said, and is essential to the Mars 2020 Rover mission. Mission scientists want the rover to explore what was an ancient river delta, collecting samples that will later be returned to Earth. But that terrain also is treacherous for landing a spacecraft, which necessitated a new system for landing places that previously were inaccessible.
After Perseverance entered the Martian atmosphere at almost 12,500 miles per hour, it deployed a parachute to slow its descent and the LVS began taking photos, matching the images with orbital maps of Jezero Crater. This Terrain Relative Navigation System was critical as the craft neared the ground and jettisoned the parachute. During the rover's powered descent to the surface, the algorithms and software in the spacecraft diverted the landing as necessary to avoid any hazards.
In addition to software, the system required the team to design a special, high-speed computer. Johnson explained that space computers are rugged and built to withstand the harmful effects of radiation, but run slowly relative to a typical PC back on Earth. The new computer vision system, however, requires a computer that can process images in real time.